When does tissue become an issue?

The discussion in the article, Body of Research - Ownership and Use of Human Tissue, about the issue over ownership of donated tissue inspires a similar train of thought on documents containing personal information about a persons life and function in society. If there is a debate about the rights an individual has over any body parts or tissues they may have donated, how should we approach private documents after the person no longer has an attachment to these documents? In other words, once a person dies, do their private records still need to be protected if those records can help those still living? If a tissue sample that was once under the protection of the principles that insure certain rights over the relationship a person has with their body is void once separated from that body, can the same be said for documentation? In other words, when do the laws that protect certain documents become inappropriate?